This invention relates to a contact sensor, and particularly to the contact sensor which is fixed to an axle of a machine tool or an apparatus of measurement, which the sensor has one set of electric contacts provided axially on a bridge member and a movable probe.
A conventional contact sensor has three sets of electric contacts and one set of the contacts has two electric contacts comprised by two ball bearings and an arm member, and a probe is supported at three points on three pairs of the electric contacts by three arm members as shown in the Japanese patent application laid open No. 49-94370 (94370/74). Therefore, the conventional electric contacts are totally provided six electric contacts thereon, and has a fault that the reliance of the sensor is reduced. The three arms extended radially from the center of the top of the probe and each arm is supported on a V-shape groove of a pair of the ball bearing of the electric contacts. By these three points support of the probe, there is other fault that precision of repetition operation of the contact sensor differ due to direction of measurement of an object, therefore, when the object is measured, if the direction of the object is not decided, a value of the measurement is brought about a change. And insulating member as a insulating wall must be provided between each ball bearing as the electric contacts, and three arms must be radially provided to touch the ball bearings. Therefore, the structure of the conventional contact sensor is very complex and the cost for manufacturing the sensor is highly increased.